1. Field of the Invention
The present invention relates to a numerical control device, and more particularly to a numerical control device which interrupts machining at designated time.
2. Description of the Related Art
The present invention relates to a numerical control device, and more particularly to a numerical control device which interrupts machining at designated time.
Heretofore, a numerical control device disclosed in Japanese Patent Laid-Open No. 2009-181174, as a numerical control device for interrupting a machining tool before designated time. The numerical control device, disclosed in Japanese Patent Laid-Open No. 2009-181174, predicts an execution block at earthquake occurrence prediction time, specifies a block as an operation stop block, in which a spindle stops or a tool or a workpiece is moved in a fast forward manner, among the blocks from currently executing block to the execution block at the prediction time, and stops the machine at the operation stop block for the sake of safely stopping the machining tool before the earthquake occurrence prediction time.
FIG. 7 shows a schematic flowchart of specification process of the operation stop block, to be executed in the numerical control device disclosed in Japanese Patent Laid-Open No. 2009-181174.    [Step SD01] The number of the block executing at the start is set in the operation stop determination block number B.    [Step SD02] It is determined the block with the operation stop determination block number B is a rapid traverse block, a spindle stopping block, or not. The process proceeds to Step SD 06 when the block with the operation stop determination block number B corresponds to the rapid traverse block or the spindle stopping block, while the process proceeds to the Step SD03 when not.    [Step SD03] It is determined whether the block with the operation stop determination block number B is a block predicted to be executed after the stopping designated time or not. The process proceeds to Step SD05 when the block with the operation stop determination block number B is the block predicted to be executed after the stopping designated time, and the process proceeds to SD04 when not.    [Step SD04] The operation stop determination block number B is incremented and the process returns to Step SD02.    [Step SD05] The block at the start is set to be the operation stop block, and the process ends.    [Step SD06] The current block with the operation stop determination block number B is set to be the operation stop block, and the process ends.
However, in the numerical control device described in Japanese Patent Laid-Open No. 2009-181174, the nearest block to which safety stop is possible from the executing block is searched since the purpose of the numerical control device is to stop in the shortest time, so there is a problem that is impossible to machine as long as possible before the designated time.
In addition to that, in the numerical control device described in Japanese Patent Laid-Open No. 2009-181174, the acceleration/deceleration time and the execution order of the program is not considered, so the stop block is designated with poor accuracy, such that there is a problem that it is impossible to predict the block to be executed after long time.